Environmental Influences on the Relationship between Fall and Spring Vigor in Hairy Vetch

Hairy vetch ( Vicia villosa Roth) is a commonly grown legume cover crop in the United States. Critical breeding goals for the species include increasing early fall vigor and spring biomass production. To ascertain genetic improvement for these traits, we explored the relationship between fall and spring vigor. Moreover, we evaluated the variation in genotypic performance across multiple environments and assessed how weather variables affected germplasm performance. The relationship between fall and spring vigor differed by winter weather conditions. In warmer locations, top‐performing genotypes in the fall were the top performers in the spring, allowing simultaneous selection for both traits of interest. Environments with colder winter conditions, however, did not show linear relationships between fall and spring vigor. At cold sites, the most and least vigorous plants in the fall tended to underperform in the spring. Results suggest that fall vigor is not a linear predictor of spring vigor in cold environments, and consequently, breeding programs should screen and select for both traits in cold climates. Genotype × environment interaction (GE) heavily contributed to spring vigor performance. In our dataset, days below freezing without snow cover, days below freezing, minimum daily temperature, and freezing degree days were related to the signal in GE. As a result, breeding programs would benefit from dividing selection sites according to the severity of winter conditions.